Author's purpose and POV

I think that Emily Rodda wrote this story to tell
every one."You don't have to be big and strong
to be brave.Just trust yourself and you can
acheive any thing."

Questions?

Why did you make rowan so different?
Why was strong John's stength destroyed?
Why was Brodan left with out family?
Why is R owan unwanted?
Why base the story on a riddle?